The present invention pertains generally to deep soil subterranean mixing or processing. In particular, the invention provides an improved system used to drive a subterranean soil processing/mixing tool.
Deep soil mixing systems have been used to create subterranean structures such as building foundations, bridge and overpass footings, as well as subterranean supports for airport runways, levees and sea walls. The deep soil processing/mixing systems include the systems described in the following U.S. patents, all of which are incorporated herein by reference: U.S. Pat. Nos. 4,793,740; 4,958,962; 5,396,964; 5,890,844; 6,183,166; 6,241,426; 6,988,856 and 7,377,726. These prior art systems have inherent, significant limitations imposed by the drive system used to rotate the soil processing tool. These limitations include the amount of torque applied and the horizontal “reach” attainable by the crane.
These limitations imposed on prior art deep soil processing/mixing systems are primarily a result of the perceived requirement to use “top drive” systems with multi-sectional round Kellys. A “top drive” system is typically a heavy, hydraulic drive unit positioned high above ground level (usually 50-100 feet). The drive unit is connected to the top of a round Kelly section and moves downwardly with the Kelly. When multi-piece round Kelly bars are used, the drive unit is separated from each Kelly piece slightly above ground level. The drive unit is then hoisted up to be connected to the top of the next round Kelly piece. This process is time consuming and expensive. These top drive units create large amounts of torque (30,000 to 40,000 ft. lbs.) that must be resisted by the lead column, the crane boom or both. The heavy drive unit positioned high above ground level and producing large amounts of torque creates a top-heavy, vibration prone system with limitations on applied torque. The top drive systems require the use of relatively heavy cranes to support the drive system and to resist the applied torque and vibrations.
The prior art also includes the use of multi-sectional Kellys having a square cross-section (or other polygonal cross-sections). Such Kellys are capable of transmitting more torque and may utilize either a top drive or a bottom drive wherein a rotary drive table applies the torque. Multi-sectional square Kellys are also known in the art (see U.S. Pat. No. 5,396,964 at column 10, line 54—column 11, line 10). The problem with multi-sectional square Kellys is that the adjacent sections become misaligned after several uses and are unable to pass downwardly through the rotary drive table.
The present invention, for the first time, provides a bottom drive system utilizing a novel roller design that overcomes the inherent limitations of the prior art noted above. The bottom drive system of the invention is capable of generating and effectively using 200,000 ft. lbs. of torque, about 5 times as much as the prior art. The novel bottom roller drive system overcomes the problem of misaligned square Kellys and eliminates the need for a heavy “top drive,” used with round or square Kellys, reducing the weight required of the crane and allowing a greater horizontal “reach” of the crane. The novel bottom roller drive greatly reduces, and in some cases eliminates, the intense vibrations otherwise induced in the crane boom, lead column and Kelly bar by the prior art top drive.
A primary object of the invention is to provide a bottom roller drive system for a subterranean soil processing tool utilizing square (or other polygonal) cross-section Kellys and using about 5 times as much torque as prior art drive systems.
A further object of the invention is to provide a bottom roller drive system usable with square Kellys wherein misaligned Kellys are able to move upwardly and downwardly through the drive system.
Another object of the invention is to provide a novel bottom roller drive system for a subterranean soil processing tool which reduces the weight of the crane and which allows a greater horizontal “reach” of the crane.
Other objects and advantages will become apparent from the following description and drawings.